A068882 - OEIS

%I #10 Aug 17 2018 10:49:35

%S 1,3,6,10,21,36,45,78,105,210,276,325,496,561,630,703,741,903,1830,

%T 2145,2701,5050,6105,6903,8385,9870,10585,12561,14365,18145,18721,

%U 23436,25878,29890,30381,32385,36585,38503,38781,41616,47278,50721

%N Triangular numbers with property that digits alternate in parity.

%H Giovanni Resta, <a href="/A068882/b068882.txt">Table of n, a(n) for n = 1..10000</a>

%e 1830 is a term as 1, 8, 3 and 0 have odd and even parity alternately.

%t altQ[n_] := n < 10 || Union[ Total /@ Partition[ Mod[ IntegerDigits@n, 2], 2, 1]] == {1}; t[n_] := n (n + 1)/2; Select[ t@ Range@ 400, altQ] (* _Giovanni Resta_, Aug 17 2018 *)

%Y Cf. A068876, A030152.

%K nonn,base

%O 1,2

%A _Amarnath Murthy_, Mar 19 2002

%E More terms from _Sascha Kurz_, Mar 23 2002